Frost Dates: First and last frost dates for casa grande, az
What's a safe temperature for tender plants? When the nightly temperature falls, frost can form, even above 32°, because the air is colder high above the ground and the frost can form up there and then fall down onto your garden and do some damage, even if it's 36° on the ground. So many factors come into play, including wind, concrete, houses, trees and other structures, etc etc etc. Because of all this, you might want to consider 36° as "the danger zone".
In your average springtime, you have a 90% chance that there will be no 36° nights by April 19. In other words, you can pretty much count on being safe from frost by that day. But we want to get those tomatoes in the ground as soon as possible, right? We see that there's still an 80% chance of 36° on February 22, so we don't dare plant that early. We wait a few days and by March 16 we are at the 50/50 point. At this point, we are close and we can start watching the weather forecast. If the upcoming week's forecast doesn't show below 40°, then it's probably okay to risk planting out your plants.
| Temperature | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| Last 16° | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| Last 20° | Dec 20 | -- | -- | -- | -- | -- | -- | -- | -- |
| Last 24° | Feb 7 | Jan 24 | Jan 13 | Jan 2 | Dec 20 | Nov 28 | -- | -- | -- |
| Last 28° | Feb 26 | Feb 16 | Feb 8 | Feb 2 | Jan 26 | Jan 20 | Jan 13 | Jan 4 | Dec 18 |
| Last 32° | Mar 31 | Mar 18 | Mar 9 | Mar 1 | Feb 22 | Feb 15 | Feb 7 | Jan 28 | Jan 16 |
| Last 36° | Apr 19 | Apr 8 | Mar 30 | Mar 23 | Mar 16 | Mar 10 | Mar 2 | Feb 22 | Feb 10 |
The charts on this page show the probabilities of receiving a certain temperature on a certain day. Some examples that might help:
- You have a small 20% chance of getting 32° by November 13.
- There is a 50% chance of being hit by a 32° frost starting around November 25
- You have a 80% chance of seeing 32° by December 7
- Said another way, you have a 1 in 5 chance at making it to that day without a 32° night.
| Temperature | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| First 16° | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| First 20° | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| First 24° | Dec 7 | Dec 18 | Dec 28 | Jan 6 | Jan 18 | -- | -- | -- | -- |
| First 28° | Nov 19 | Nov 27 | Dec 4 | Dec 9 | Dec 14 | Dec 19 | Dec 25 | Jan 1 | Jan 15 |
| First 32° | Nov 7 | Nov 13 | Nov 18 | Nov 22 | Nov 25 | Nov 29 | Dec 3 | Dec 7 | Dec 14 |
| First 36° | Oct 26 | Nov 2 | Nov 6 | Nov 10 | Nov 14 | Nov 18 | Nov 22 | Nov 27 | Dec 4 |
Data is provided by the NOAA National Centers for Environmental Information.